Hey i was 5'1 1/2 and now i'm like 5'2 1/2 in a year . im 16? how can i stop growing ?

Many factors: There are many factors that go into growth. Now how tall are your parents? You may just be a slow grower. You still have many years to grow so do not worry make sure your eat healthy and then just nature take its course. Be patient

Nothing : You can do. But why do you want to stop growing? It is likely that you won't grow much after the age.